1. Field of the Invention
The present invention is broadly concerned with therapeutic proteinaceous substances produced by Staphylococcus, and with methods of inhibiting the growth of eucaryotic or procaryotic cells using these substances. More particularly, the invention in its preferred form is directed to BacR1, a 3.4-kilodalton therapeutic proteinaceous substance produced by Staphylococcus aureus UT0007. The sequence of the BacR1 gene is set forth in SEQ ID No. 2, while the sequence of the BacR1 peptide is set forth in SEQ ID No. 3.
2. Description of the Related Art
Bacteriocins and colicins are antimicrobial agents produced by gram-positive bacteria and gram-negative bacteria, respectively. Each of these agents inhibits or kills species which are closely related to the organism producing it (Jack et al. 1995. Microbiol. Rev. 59:171-200). Colicins generally have (1) a narrow range of antimicrobial activity, (2) bacteriocidal activity, (3) a protein component expressing the antimicrobial activity, (4) the ability to attach to specific cell-surface receptors, (5) plasmid-borne genetic determinants, and (6) immunity mechanisms to avoid cell suicide (Tagg et al. 1976. Bacteriol. Rev. 40:722-756).
Bacteriocins and bacteriocin-like inhibitory substances are similar in nature to colicins. However, they do not possess all of the colicin characteristics noted above (Jack et al. 1995. Microbiol. Rev. 59:171-200). They generally exhibit a broad range of antimicrobial activity against gram-positive bacteria, and in some cases also inhibit gram-negative species. Genes encoding bacteriocin usually are arranged in operons located on plasmids. For example, the operons encoding the bacteriocins nisin (Engelke et al. 1992. Appl. Environ. Microbiol. 58:3730-3743) and epidermin (Augustin et al. 1992. Eur. J. Biochem. 204:1149-1154), in addition to containing the respective bacteriocin structural genes, contain genes responsible for post-translational modifications, processing, cellular export, and host cell immunity. Most bacteriocins are small cationic peptides that are relatively heat stable, sensitive to proteolytic enzymes, non-antigenic, and very hydrophobic (Jack et al. 1995. Microbiol. Rev. 59:171-200; Tagg et al. 1976. Bacteriol. Rev. 40:722-756). High molecular weight bacteriocins consisting of proteins complexed with lipids and/or carbohydrates also have been identified (Jack et al. 1995. Microbiol. Rev. 59:171-200).
The majority of research regarding bacteriocins has focused on those produced by the lactic acid bacteria, since these bacteriocins have potential as food preservatives (Hurst et al. 1981. Adv. Appl. Microbiol. 27:85-123). Additionally, several staphylococcal bacteriocins have been identified, including the staphylococcins 412 (Gagliano et al. 1970. J. Bacteriol. 104:117-125), 462 (Hale et al. 1973. Antimicrob. Agents Chemother. 4:634-640), C55 (Dajani et al. 1970. Infect. Immun. 1:485-490), and BacR1 (Rogolsky et al. 1977. Infect. Immun. 15:726-732). Although the bacteriocin BacR1 has been identified, it has not been isolated or well characterized. Furthermore, no pragmatic uses for BacR1 have been proposed in the prior art. For example, the Rogolsky et al. paper reported a maximum specific activity for the crude preparation of only 46 AU/mg; moreover, the sequence of the BacR1 gene and the corresponding peptide have not been identified.